A statistical evaluation of ground water chemistry from the west coast of Tamil Nadu, India

Abstract

Ground water chemistry in the coastal area between Kollamkode and Kanyakumari has been studied. Quality assessment was made through the estimation of pH, EC, salinity, DO, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, PO₄3-, NO₃⁻, NO₂⁻, HCO₃⁻, and total hardness. The wells in general showed high values of conductivity, salinity, chloride, hardness and calcium. The chemical relationship exhibited by Piper’s diagram suggests that the groundwater mainly belongs to the hydrochemical facies Na-Ca and Cl-SO₄-HCO₃. Samples from the coastal fringe zone seldom represent fresh groundwater. Seasonal landward shift of freshwater-saltwater interface was observed throughout the coastal zone. It was found that Na⁺ and Cl⁻ are the dominant cation and anion in the area. Correlation analysis showed perfect correlation between EC and TDS, reveals that EC is a measure of dissolved solids in ground water. The clusters defined by Q-mode analysis reflect the spatial distribution of samples and the R-mode cluster conveys that salinity, TDS, EC and Na⁺ form one group. The interface zone that extends up to 200-250m from the shoreline has to be carefully exploited, after identifying the discharge and the probable zones.